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Yes, probably! But you can do it yourself without one.

Here is an example in C using libopencm3, that uses timers to trigger an interrupt used to flash LEDs https://github.com/libopencm3/libopencm3-examples/tree/maste...

that is basically a mini-os :)

You can set up a wakeup interrupt using a timer by moving a few values into a few registers. It doesn't require anything like an OS. Even tiny 8-bit microcontrollers can do this.

Sure, but putting the chip to sleep is one instruction, and programming the timer interval is only about a dozen instructions. So you don't really need an OS in this context.

There is a blurry line on the edges of "library" and "OS"; most people would put this particular example on the "library" side.